Systems employing water-based functional fluids commonly have problems resulting from the corrosion of metal components. Corrosion occurs on ferrous-type metals as well as other metals within the system. Commonly, corrosion-inhibitors are used in the functional fluid to cure these corrosion problems.
When corrosion-inhibitors are used in functional fluids, the corrosion-inhibitors may act to decrease the stability of the fluid. Instability of the functional fluid may be described as a separation of the components of the fluid, e.g. a break in the dispersion. Care must be taken to balance corrosion-inhibiting properties versus fluid stability. Fluid stability is particularly troublesome in areas having hard water in the range of greater than 100 PPM. Commonly the water used in the functional fluid is supplied from the area surrounding the system where the functional fluid will be used. For instance, a fluid for a mining application will often be prepared using the water from the mine. This water often has a high degree of hardness, sometimes greater than 200 ppm.
It is desirable to have corrosion-inhibitors that prevent corrosion of metals within the system without detrimentally affecting fluid stability. It is particularly desirous to have corrosion-inhibitors which work in hard water.